The headquarters of the Defense Ministry in Yongsan-gu, Seoul. (The Korea Herald DB)

The military is conducting an investigation into a leak of personal information of agents assigned to an intelligence unit tasked with spying on North Korea, sources said Saturday.

The Korea Defense Intelligence Command discovered about a month earlier that classified information, including personal data of its agents stationed overseas, had been leaked, prompting an investigation by the Defense Counterintelligence Command.

The leaked information is said to have included those on official cover agents working as diplomats, as well as undercover agents, with some agents reportedly returning home due to concerns over their identities being exposed.

Military authorities have discovered that many of the agents affected by the leak were tasked with operations related to North Korea, and officials have detected signs the leaked data was directed to the North.

Authorities are investigating a civilian official at the Korea Defense Intelligence Command over the leak after discovering that classified files had entered the official's personal laptop.

Authorities believe the laptop to be the source of the leak, but the official has reportedly claimed that the computer had been hacked.

It is not the first time the Korea Defense Intelligence Command has faced such a major data leak. In 2018, authorities discovered that an official at the command had been selling classified information overseas since 2013. (Yonhap)